Development and evaluation of a solid-phase enzyme immunoassay based on Andes hantavirus recombinant nucleoprotein.

Hantavirus pulmonary syndrome (HPS) with high mortality rate has been reported in five countries in South America. Rapid accurate methods are important both for monitoring acute infections and for epidemiological studies. The Andes virus nucleoprotein amino acid sequence has a high identity percentage compared with other sequences of this region and has been chosen for the development of diagnostic reagents. Andes nucleoprotein expressed in Escherichia coli was applied as antigen in IgG, IgA and mu-capture IgM enzyme-linked inmunosorbent assays (ELISAs). An evaluation of this reagent was conducted to establish its usefulness for differential diagnosis of HPS and seroprevalence studies. Samples from 135 reverse transcription (RT)-PCR-confirmed HPS cases, 77 individuals with other respiratory infections and 957 healthy inhabitants from endemic and non-endemic areas were analysed. The hantavirus-infected patients had an early and strong IgM, IgG and IgA serum antibody response, in most of the cases as early as 1, 7 and 1 days following onset of symptoms, respectively. IgM and IgG detection showed a specificity and sensitivity of 100%. Andes-specific IgM antibodies were found in all patients in the first available sample, which remained detectable for at least 43 days. Specific IgA antibodies were also detected in saliva of patients with acute HPS. The short duration of the disease and the risk for contacts due to person-to-person transmission of Andes virus necessitate the use of highly sensitive tests which might lead to earlier detection of infected people and improve the treatment and management of patients with HPS.

Hantavirus pulmonary syndrome outbreak in Argentina: molecular evidence for person-to-person transmission of Andes virus.

An increase of Hantavirus Pulmonary Syndrome (HPS) cases around a southwestern Argentina town and in persons living 1400 km away but in contact with those cases was detected during the spring of 1996. In order to evaluate person-to-person transmission we compared the homology of PCR-amplified viral sequences of 26 Argentine and Chilean cases. Sixteen of them were epidemiologically linked cases and had the same sequence (Epilink/96) in the S segment 3' noncoding region and in the M segment partial G1 and G2 region (a total of 1075 nucleotides). Contrarily, two geographical and contemporary but nonepidemiologically related cases differed from Epilink/96 in the compared regions. No significant differences, such as glycosylation or hydrophilic pattern, were found between Epilink/96 and the other sequences. Nucleotide and deduced amino acid sequence homologies between samples from southern Argentina and Chile ranged from 90.9 to 100% and 96.4 to 100%, respectively. Phylogenetic analysis revealed that all the analyzed southwestern viruses belong to the Andes lineage. Although human infection principally occurs via inhalation of contaminated rodent excreta, our results with Andes virus show the first direct genetic evidence of person-to-person transmission of a hantavirus.

Genetic diversity, distribution, and serological features of hantavirus infection in five countries in South America.

Since 1995 when the first case of hantavirus pulmonary syndrome (HPS) was reported in Patagonia, there have been more than 400 cases of HPS reported in five countries in South America. The first case of HPS was associated with Andes (AND) virus. In this study, we report on the genetic diversity, geographical distribution, and serological features of hantavirus infection in six countries in South America based on 87 HPS cases from Argentina, Bolivia, Chile, Paraguay, and Uruguay. An early immunoglobulin M (IgM), IgA, and IgG humoral response was observed in almost all HPS cases. The IgM response appears to peak 1 or 2 days after the onset of symptoms. Peak IgG antibody titers occur mostly after the first week. Low IgG titers or the absence of IgG was associated with higher mortality rates. The IgA response peaks around day 15 and then rapidly decreases. The results of phylogenetic analysis based on partial M-fragment G1- and G2-encoding sequences showed that HPS cases from the five countries were infected with viruses related to AND or Laguna Negra (LN) virus. Within AND virus-infected persons, at least five major genetic lineages were found; one lineage was detected in Uruguayan and Argentinean cases from both sides of the Rio de la Plata river. Two Paraguayan patients were infected with a virus different from LN virus. According to the results of phylogenetic analyses, this virus probably belongs to a distinct lineage related more closely to the AND virus than to the LN virus, suggesting that there is probably an Oligoryzomys-borne viral variant circulating in Paraguay. These studies may contribute to a better understanding of hantavirus human infection in South America.